lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 1 Nov 2017 12:05:55 +0000 From: Mark Rutland <mark.rutland@....com> To: Laura Abbott <labbott@...hat.com> Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, Catalin Marinas <catalin.marinas@....com>, Kees Cook <keescook@...omium.org>, Will Deacon <will.deacon@....com> Subject: Re: [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks On Tue, Oct 31, 2017 at 04:56:39PM -0700, Laura Abbott wrote: > On 10/26/2017 02:09 AM, Mark Rutland wrote: > > In Prague, Kees mentioned that it would be nice to have a mechanism to > > catch bad __{get,put}_user uses, such as the recent CVE-2017-5123 [1,2] > > issue with unsafe_put_user() in waitid(). > > > > These patches allow an optional access_ok() check to be dropped in > > arm64's __{get,put}_user() primitives. These will then BUG() if a bad > > user pointer is passed (which should only happen in the absence of an > > earlier access_ok() check). > Turning on the option fails as soon as we hit userspace. On my buildroot > based environment I get the help text for ld.so (????) and then a message > about attempting to kill init. Ouch. Thanks for the report, and sorry about this. The problem is that I evaluate the ptr argument twice in __{get,put}_user(), and this may have side effects. e.g. when the ELF loader does things like: __put_user((elf_addr_t)p, sp++) ... we increment sp twice, and write to the wrong user address, leaving sp corrupt. I have an additional patch [1] to fix this, which is in my arm64/access-ok branch [2]. Thanks, Mark. [1] https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?h=arm64/access-ok&id=ebb7ff83eb53b8810395d5cf48712a4ae6d678543 [2] https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/access-ok
Powered by blists - more mailing lists